BREED DIFFERENCES IN RESISTANCE TO A DEFICIENCY OF VITAMIN Bi IN THE FOWL

The breeds and varieties of domestic fowls differ in size and shape of body, in structure and color of plumage and skin, in variation of the skeleton, and in the modification of structures, such as the comb and spurs, arising from the skin. Apart from colors, the differentiation of the breeds at the time of their establishment was apparently based upon morphological characters. A few differences between breeds in physiological characters, such as broodiness and color of Qgg, are now known, but it is not impossible that the present comparative freedom of Leghorns from broodiness and the ability of the same breed to lay white-shelled eggs may have resulted largely from artificial selection for those physiological characters as for other distinguishing breed characteristics. This paper reports an association between breed characteristics and an interesting physiological character—resistance to a deficiency of vitamin Bi. The first indication that White Leghorns require comparatively little vitamin Bi, or through differential storage of it, or by other means, are markedly resistant to polyneuritis, was put forward by Nichita and Iftimesco {9)? On a diet deficient in vitamin Bi, or lacking it entirely, one of three White Leghorns, 10 months old at the start of the experiment, showed symptoms of polyneuritis after 41 days and died in 49 days. Another was entirely unaffected and was removed from the experiment at 78 days. A third showed no symptoms till the one hundred and seventh day and for 3 weeks thereafter maintained a subacute chronic state of polyneuritis, but quickly recovered when placed on a normal diet. On the other hand, Nichita, Tuschak, and Calcef {10) found that on diets deficient in vitamin Bi six Rhode Island Reds about 10 months old showed symptoms of polyneuritis at from 7 to 19 days. Three of them were given yeast and quickly recovered, but the other three died of acute polyneuritis in 9, 18, and 21 days. In both experiments, controls on the experimental diet plus yeast were entirely normal. The experiments of Nichita and his coworkers were not set up primarily to test the two breeds as to their requirements of vitamin Bi, and unfortunately the diets used differed considerably. The diet of the Rhode Island Reds included fresh beef, glucose, and starch, whereas that the White Leghorns did not. The latter received their carbohydrates from decorticated rice. Hence, while the experiments within each breed were well controlled, the fact that the diets were not identical makes any comparison of the two breeds with respect to their